The present invention relates to measuring and monitoring fluid flow parameters and more particularly to measurement of fluid temperature and pressure accurately and reliably in a wellbore of an oil, gas, or geothermal well.
The accurate measurement of wellbore fluid temperature and pressure has been recognized as being important in the production of oil, gas, and geothermal energy. Often the fluid flow around the temperature or pressure probes, specially in deep boreholes, does not come in reasonably complete contact with the probe due to Bernoulli effect and/or debris settlement near the probes. Another reason that fluid flow contact with the probe is diminished is that generally the probe dimensions are large enough to act as a heat sink; thus, reducing the temperature of the surrounding fluid media. As a consequence temperature and pressure measurements are not accurate. Hydrocarbon exploration, production and secondary hydrocarbon recovery operations, and geothermal operations require temperature and pressure data to determine various factors considered in predicting the success of the operation, and in obtaining the maximum recovery of energy from the wellbore.
In hydrocarbon exploration and recovery operations, borehole temperature and pressure measurements are two of the key parameters that give indications of a well""s productivity potential. Therefore, accurate measurement of borehole temperature and pressure is of paramount importance. The accurate measurement of temperature and pressure changes in well fluids from various boreholes into a formation provides indication of the location of injection fluid fronts, and the efficiency with which the fluid front is sweeping the formation.
Numerous techniques comprising of lowering sensors into the borehole at desired location have been devised for periodic measurement of wellbore temperature and pressure. Such periodic measurement techniques are inconvenient and expensive because of the time and expense involved for inserting the necessary instrumentation into the borehole. Moreover, such periodic measurement techniques are limited in scope because they provide only a representation of borehole parameters at specific times, while measurements over an extended period are desirable. Ideally, continuous monitoring of the parameters is needed by the operator. For example U.S. Pat. No. 3,712,129, teaches charging an open-ended tube with a gas until it bubbles from the bottom of the tube in order to provide the desired periodic pressure measurement.
Permanent installation techniques have been devised for continuous monitoring pressure in a borehole so as to alleviate the problems associated with periodic measurements. In one such prior art a wellbore pressure transducer and a temperature sensor having electronic scanning ability for converting detected wellbore pressures and temperatures into electronic data is installed at the location of interest in the wellbore. The measurement data is transmitted to the surface on an electrical wire. The electrical wire is attached to the outside of the tubing in the wellbore, and the pressure transducer and temperature sensor are mounted on the lower end of the production tubing. This system has not been well accepted in the industry, partially because of the expense and high maintenance of the surface electronics required over an extended period of time. The reliability of the wellbore electronics is considerably reduced in high temperatures, pressures and corrosive fluid environment in the wellbore that substantially increases the expenses. U.S. Pat. No. 3,895,527 teaches a system for remotely measuring pressure in a borehole utilizing a small diameter tube whose one end is exposed to borehole pressure and the other end is coupled to a pressure gauge or other pressure detector located at the surface. U.S. Pat. No. 3,898,877, discloses a system of measuring wellbore pressure which uses a small diameter tube, and an improved version of such a system is disclosed in U.S. Pat. No. 4,010,642. The teachings of ""642 patent have considerably improved the technology of measuring pressure in a borehole, because the lower end of the tube extends into a chamber having at least a desired fluid volume. However, teachings of patent ""642 do not disclose measurement of both temperature and pressure at the desired location in the wellbore. An operator may be able to estimate wellbore fluid temperature by extrapolating from assumed temperature gradient data and pressure measurements taken at the surface, and/or by estimating an average temperature for the borehole from previously obtained drilling data. The estimated temperature may be used to determine a test fluid correction factor, which may then be applied to more accurately determine the wellbore pressure. It is long recognized, however, that still accurate temperature information is not being obtained, and therefore, the correction of pressure readings based on inaccurate temperature estimates results in errors in the pressure readings obtained by the technique of utilizing such a small diameter tube.
In addition to inaccuracy of the extrapolated temperature, the true temperature within a well varies with wellbore depth and, gas release and/or xe2x80x9cfreezingxe2x80x9d and other variations that may occur at particular depths. As a consequence wellbore temperature or pressure in most boreholes cannot be reliably and economically measured, and one cannot maximize recovery of energy from the borehole. U.S. Pat. No. 5,163,321 patent teaches a system which comprises a single small diameter tubing extending from the surface of the well to the desired wellbore test location. Pressure at the location of the tube end in the wellbore is then extrapolated by the corresponding surface reading. A thermocouple at the same location measures the temperature and is conveyed to the surface by means of a wire or by fiber optic means. Apparently, reliance on extrapolation of the pressure data obtained at the surface to determine pressure at the specific location in the wellbore makes the measurements inaccurate. Furthermore, the temperature measurement at the location of interest is subject to temperature anisotropy caused by the fluid flow. The temperature at the location of interest varies because of fluid emanating from different parts of the wellbore, and also due to pressure differential around the probe because of Bernoulli effect, resulting in poor fluid contact with the probe.
An innovative temperature and pressure sensing device is described in this invention that overcomes aforementioned deficiencies of inadequacy of good fluid contact with the sensor and uniformity of the fluid contact with the sensor. The disclosed temperature and pressure sensing device can be used for continuous monitoring of the temperature and pressure in locations where accurate measurements in flowing fluid is desired.
A temperature sensing device removably disposed in conduit means which provides fluid flow in a production process comprising a temperature sensor capable of detecting temperature in the fluid flow comprising a face having a surface roughness capable of providing turbulence to the fluid flow, wherein the face with surface roughness is made of thermally conductive material; a temperature probe in thermal connection with the face; and a thermal insulating barrier surrounding the temperature probe and connected to the face, the thermal insulating barrier containing a passageway for providing signaling means; a tubular member containing passageway continuing from the thermal insulating barrier for providing signaling means, the tubular member connected to the insulating barrier; signaling means disposed in the passageway of the tubular member for communicating the temperature detected by the temperature probe to a remote monitoring device; thermal insulating means disposed around the tubular member; and connecting means for detachably connecting the thermal insulating barrier to the insulating means.